Overview of Nasopharyngeal Cancer
Many factors may influence the development of nasopharyngeal (NP) cancer, including diet, viruses and genetic susceptibility. In some areas of the world, such as North Africa and Southern China, the occurrence of nasopharyngeal cancer is common. It is believed that in these areas diet may play a role in the development of this disease. Most people in these areas make and consume salt-cured meats and fish, and it is thought that cooking these foods releases nitrosamines into the air which distribute over the mucous membranes of the nasopharynx (nasopharyngeal mucosa), producing changes which increase the risk of developing cancer.
Viruses such as Epstein-Barr virus (EBV) may also be a causative agent in the development of nasopharyngeal cancer. EBV is a common virus that lies dormant in most people. It has been associated with certain cancers, including Burkitt's lymphoma, immunoblastic lymphoma, and NP carcinoma. It has been found in specimens of NP cancer and has been shown to be capable of causing malignant change in test tube cells.
Lastly, genetic susceptibility may play a role in that individuals with certain HLA (human lymphocyte antigen) types—specifically H2, BW46 and B17—have an increased incidence of developing the disease.
The peak incidence of NP cancer occurs in persons 40 to 50 years of age. Males outnumber females by approximately 2 to1.
Nasopharyngeal carcinoma is divided pathologically into three types:
- Type 1 or keratinizing squamous cell cancer;
- Type 2 or nonkeratinizing carcinoma; and
- Type 3 or undifferentiated carcinoma.
Undifferentiated cancers are the most common. Any of these cancers can grow, either by infiltration or by expansion. Most infiltrate into neighboring tissues. Clinically, Type 1 tumors have a greater risk of uncontrolled local tumor growth and lower potential for regional or distant spread than Types 2 or 3, which have a high rate of metastasis to regional lymph nodes.
The most common symptom of NP carcinoma is a mass in the neck. Other symptoms include alterations in hearing, ringing in the ears (tinnitus), nasal obstruction and pain.